Microsoft plans to release a test version of the next version of Windows on Wednesday morning, according to a source familiar with the company's plans.

The Beta 1 version of Windows Vista isn't expected to have the look and feel of the final operating system. However, it is expected to reflect key changes that Microsoft is making under the hood of its flagship operating system. The test version is expected to be limited, at least initially, to developers and technical audiences.

Microsoft said on Friday that it was renaming the operating system, which had been known for years only by its code name, Longhorn. The company also promised that a long-anticipated beta version would ship by Aug. 3.

Windows enthusiast site WinBeta reported earlier Tuesday that the Beta 1 version was expected to come out on Wednesday.

A more feature-complete test version is expected to arrive by early next year, as Microsoft aims to have the final release of Windows Vista available in time to be on PCs that ship during next year's holiday shopping season.

Previous Next Vista has changed significantly since Microsoft Chairman Bill Gates first showed an early version of the then-Longhorn in October 2003. The company has changed the way it is implementing a new Web services architecture, known as Indigo, and a new graphics engine, dubbed Avalon. It has also delayed a new file system, known as WinFS, that had been slated to be part of the OS.

Among the more visible changes in the OS are a new means of searching for files, as well as virtual folders that contain all of the documents that match a specific criteria, such as "edited in the last week" or "created by Mary."

The company is also working on business-oriented changes, such as making it easier to set up and manage a stable of Windows Vista-based PCs.

Also planned are improved home networking, stricter parental controls and a host of new laptop-related features, though not all of these changes may be visible in the test version due out Wednesday